Compression encoding refers to a series of signal processing techniques that either transmit digitalized information through a communication line, or store digitalized information in a storage means in an adequate format. Targets of compression encoding may include audio (or sound), video (or image), text, and so on. Most particularly, a technique of performing compression encoding targeting video (or images) is referred to as video image compression. The general characteristic of a video image is that a video image carries spatial redundancy and temporal redundancy.